how to do real time programs?

frostmagic · 02-02-2004, 02:53 AM

how do i implement it using general linux? is it possible to do it?
if possible can some one tell me how to write it?

Or must i use a rtlinux to do it?

llama_meme · 02-02-2004, 07:56 AM

It totally depends on how strict your real time requirement is. If you're writing a hard real time app, an ordinary Linux kernel may not be a good choice. If you're writing a soft real time app, it could work quite well. In the end you just have to try it and see. This looks quite informative: http://www.metrowerks.com/pdf/Metrow...as_RTOS_v2.pdf

Alex

jtshaw · 02-02-2004, 09:20 AM

I took a closer look at your timing schemes and since .5 second is the tightest you need you can probably handle the just fine. In fact, if you are using a linux kernel with the enhanced real time clock you could set the frequency of that and use it for timing. I am not sure exactly how that works but mplayer uses that for video timing so you can probably look at there code.

What kind of server is this? As I said before, only use timing to define a network protocol if there is absolutely no other way.

frostmagic · 02-02-2004, 10:42 AM

I data - 13888 usecs
P data - 2777 usecs
B data - 555 usecs

tighest is .5 secs?

hmm , it a udp protocol server
i comparing the system time with the time above everytime i send

jtshaw · 02-02-2004, 10:53 AM

oh duh... I don't know where I get .5 seconds from.

I am not sure what the resolution of the rtc is, but 555 usecs is pretty tight timing you could easily miss if the kernel decides it needs to do something else. If I personally had to have timing like that I would write an RTLinux kernel module. But that doesn't mean that you could possibly do it another way.

Is there something external that is dictating that timing?